Field of the Invention
The present disclosure relates generally to wireless power transfer. More specifically, this disclosure relates to methods and apparatus for controlling wireless power transfer between power transfer units and power receiving units to provide high efficiency power transfer.
Description of the Related Art
In general, a power transfer unit (PTU) wirelessly transmits power to a wireless receiving unit (PRU) via a wireless field generated by the PTU. In order to help ensure that the PRU receives sufficient magnetic field strength while staying within its design constraints and voltage withstanding capability, the PTU may receive one or more communications from the PRU relating to a rectified voltage at the PRU. The rectified voltage may correspond to the induced voltage received wirelessly at the PRU from the PTU that is being transferred to a load of the PRU. Accordingly, to make the wireless power transfer most efficient, the PTU adjusts its transmit current based on the received rectified voltage. The transmit current may be adjusted to change the wireless field such that the received rectified voltage approaches a target voltage at the PRU. Thus, to obtain the highest efficiency possible in the power transfer (e.g., to approach the target voltage), the rectified voltage as received from the PRU at the PTU must be indicative of the induced voltage received by the PRU. However, as PRUs become more involved or sophisticated, the rectified voltage becomes less useful as an actual measure of the induced voltage that is received by the PRU. Accordingly, alternate parameters are needed from the involved or sophisticated PRU that accurately represent the induced voltage received by the PRU so the PTU can adjust its transmit current and the wireless field to maximize power transfer efficiencies and to stay within design/spec constraints. Thus, there is a need for methods and apparatus for identifying the induced voltage at the PRU and providing it to the PTU.